Manufacture of vacuum tubes



Feb. .16, 1926. 1,573,317

' W. G. HOUSKEEPER MANUFACTURE 0F VACUUM TUBES Filed June 2, 1922 mum //7l/P/7/0K' W////'am 6'. flows/rea er Patented Feb. 16 1926.

UNITED STATES PATENT OFFICE.

G. HOUSKEEPER, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 013 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MANUFACTURE OF VACUUM TUBES.

Application filed June 2,

To all whom it may concern:

Be it known that I, WILLIAM G. Hoos- KEEPER, a citizen of the United States, residing at New York, in the county of New York, State of New York, have invented certain new and useful Improvements in the Manufacture of Vacuum Tubes, of which the following 'is a full, clear, concise, and exact description.

This invention relates to the exhaustion of vacuum tubes and pertains especially to the simultaneous evacuation of several tubes.

In the manufacture of vacuum tubes, it is customary to attach a plurality of tubes to be exhausted to the header of a pumping apparatus and to remove the gases therefrom simultaneously. After the gas within the tubes has been removed, the grids and anodes are heated by bombardment with electronsto drive out the occluded gases. To accomplish the bombardment of these electrodes, a space current is established between the cathode and other electrodes of each tube. Because of the high impedance between the cathode and the other electrodes due to the evacuated condition of the tube, a relatively large difference of potential is required to establish the space current. The issuance of the occluded gases from the electrodes, however, decreases the impedance of the space current path, making it necessary to reduce the potential differenoe between the electrodes to prevent overheating. I

Furthermore, the condition of the electrodes within each tube, determines the energy which must be applied thereto in order to establish the space current. Thus, if the electrodes are slightly oily from handling duringassembly, more energy is re quired than if the electrodes are clean.. Also the length of filament in each tube determines the energy necessary to heat it to the proper degree to establish its bombarding current. It has been the custom heretofore to utilize a separate set of circuits for each tube and to ad ust these circuits to meet the electrical requirements. Such an arrangement necessitates numerous adjustments and consequently requires considerable time as each tube has to be adjusted independently of the others.

It is an object of this invention to supply to the electrodes of a plurality of vacuum tubes simultaneously the energy necessary 1922. Serial N0. 565,301.

to establish a bombarding current in each tube between the electrodes of the tube.

Another object is to reduce to a minimum the adjustments necessary for COlltIOlllllg the bombarding current in a plurality of tubes being simultaneously evacuated.

Another object of the invention is to uniformly heat the cathodes of the tubes of a set under exhaustion regardless of the lengths of the individual filaments.

One embodiment of the invention is disclosed in the accompanying drawing wherein the filaments of a set of tubes are inductively connected in series with a source of alternating electrical energy and wherein the space current for each tube of the set is supplied from a direct current source.

A group of vacuum tubes to be exhausted is connected with a header 2 of an exhaust apparatus, not shown. The filaments 3 of tubes 1 are inductively connected by means of windings 4 and 5, and- 6 and 7 with a source of alternating current 8. In circuit with source 8 and winding 7- is a variable resistance 9. The grids and anodes 10 and 11 of the tubes 1 are electrically connected and the grid and anode of the first tube from the left are connected to the middle point of the winding 4 of the filament circuit of the second tube, the grid and anode of the second tube being connected to the middle point of the winding 4 of the filament circuit of the third tube. The grid and anode of the third tube are connected through a variable resistance 12 to the positive brush of a D. C. generator 13, the negative brush of which is connected to the middle point of the winding 4 of the filament circuit of the first tube. Switches 14 are provided by means of, which any of the windings 5 may be short-circuited and switches 15 are provided whereby the D. C. current may be shunted around any tube.

The operation of this apparatus is as follows: At the start of the evacuation of these tubes, alternating current is supplied to each of the filaments from the source 8 and direct current is supplied to the space current path of each tube from the source 13. Because of the fact that the windings 5 are connected in series, the current supplied to each of the filaments 3 will be of the same amperage and each of the filaments will be equally energized. The

potential drop across each of the space 1 current paths will be proportional to the impedance of each tube. By means of the resistance 12, the total potential drop across the tubes is adjusted to that which experiments have determined is the voltage normally necessary. The filament current of the tubes is then gradually increased by means of the resistance!) until bombardment -The additional increase of voltage in each of the other tubes is generally sufiicient to establish a bombarding current in one tube, whereupon the remaining tube is subjected to a further voltage increase, which causes the establishment of a bombarding current therein. In case the bombarding current is not established. in one of the remaining tubes, the filament current may be increased until the bombardment starts. The resistance 12 acts to prevent too great an amount of energy being supplied to the electrodes afterthe establishment of the bombarding current as the potential drop across it also increases proportionately upon the establish- -ment of the space current in each of the tubes. After bombarding current has been established in each of the tubes the filament and space current are reduced to a safe value to prevent the burning up of the electrodes. v

This arrangement greatly decreases the adjustments of currents and voltages to accomplish the bombarding of the electrodes since the space and filament currents for all the tubes are controlled by only two rheostats for the entire apparatus instead of two rheostats for each tube, as formerly. As a result, there is a saving of the operators time and also a reduction in the equipment needed for the bombarding circuits.

What is claimed is:

1. The process of simultaneously exhausting a plurality of vacuum tubes which comprises establishing a space current flow through said tubes in series, supplying equal heating currents to the cathodes of said tubes and removing from said tubes 2. The method of simultaneously exhausting a plurality of vacuum tubes which com- In witness whereof, .I. hereunto subscribe my name this 31st day of May A. D., 1922.

WILLIAM G. HOUSKEEPER. 

